Guantanamo Bay, Cuba (CNN) -- Accused terrorist Omar Khadr on Tuesday briefly addressed the 15 prospective members of a military jury that will decide the case of the youngest captive at the Guantanamo Bay, Cuba, detention facility.
Dressed in a gray suit and tie, rather than his usual white prison uniform, Khadr was asked by his attorney to stand and speak to the 11 men and four women -- all military officers -- who are the pool for a jury of at least five members.
In a soft voice, Khadr appeared to say, "How are you?" The prospective jurors sat in silence.
The 23-year-old Khadr, who was 15 when he was captured in 2002 in Afghanistan, is charged with assisting al Qaeda and with killing a U.S. Special Forces soldier with a grenade. He pleaded not guilty on Monday.
Canadian lawyer Dennis Edney, a member of Khadr's defense team, said he found the jacket and tie worn by the suspect.
"For the first time in eight years, he was allowed to feel human," Edney said about the change in attire for Khadr. "When he walked into the courtroom, everyone gasped. He was the real Omar Khadr."
Army Col. Pat Parrish, the judge in the case, said Tuesday he expected the military trial to last several weeks.
The identifies of the potential jurors have been kept secret under an order by Parrish. Six are from the Army, five from the Air Force, three from the Navy and the one Marine is a female colonel.
All were questioned Tuesday by prosecutors and Khadr's lawyer, Army Lt. Col. Jon Jackson. Once the lawyers and Parrish decide on the impartiality of each member and whether any should be excused, at least five will be selected as a jury and the formal trial will begin.
Jackson's questions focused on each potential jurist's attitudes about children charged with crimes, threats to people held in custody and the reliability of statements made under duress. The defense strategy stresses that Khadr was a child soldier forced into the fight by adults, and that after his capture, he was threatened with rape and death unless he confessed.
In a statement Tuesday, Radhika Coomaraswamy, the U.N. special representative for children and armed conflict, said child soldiers should be treated as victims and rehabilitated instead of punished. She called on Canada and the United States to reach a compromise on the Canadian-born Khadr.
"I urge both governments to come to a mutually acceptable solution on the future of Omar Khadr that would prevent him from being convicted of a war crime that he allegedly committed when he was a child," Coomaraswamy said in the statement.
Prosecutors, however, indicated they plan to introduce into evidence photos of the U.S. soldier they claim Khadr killed with a grenade just before his capture. They also are expected to show video footage that they say shows Khadr taking part in al Qaeda's assembly and deployment of roadside bombs to kill Americans.
On Monday, Parrish denied most defense motions that would have blocked the military panel from hearing previous statements by Khadr and from seeing the video footage shot on the battlefield where he was captured. The video footage was shown during pretrial motions Monday but has not been made public.
Navy Capt. David Iglesias, a former federal prosecutor and part of the Navy's Judge Advocate General's Corps, said the government would seek a life sentence if Khadr is convicted of serious charges.
Also Tuesday, a separate trial for suspected Sudanese terrorist Ibrahim Ahmed al Qosi was postponed for the day. No official explanation was provided for the delay or when proceedings might resume.
Al Qosi has pleaded guilty, admitting to conspiracy and assisting al Qaeda terrorism. Government officials have said al Qosi was deeply involved in al Qaeda operations and, among other things, served as Osama bin Laden's driver.
One potential dispute is over where al Qosi will serve his prison term and, more specifically, whether he should be allowed to intermingle with other Guantanamo detainees.
While al Qosi faces the possibility of a life sentence, he is expected to complete a far shorter prison term, followed by a return to Sudan. Federal authorities announced late Monday that the agreement on al Qosi's sentence will be made public once the agreement and military court proceedings had been reviewed.